300-710 · Question #188
A network administrator configured a NAT policy that translates a public IP address to an internal web server IP address. An access policy has also been created that allows any source to reach the…
The correct answer is D. The access policy must allow traffic to the internal web server IP address. To make an internal web server reachable from the Internet after NAT, the access policy must explicitly allow traffic to the internal, post-NAT IP address of the server, not just the public IP.
Question
A network administrator configured a NAT policy that translates a public IP address to an internal web server IP address. An access policy has also been created that allows any source to reach the public IP address on port 80. The web server is still not reachable from the Internet on port 80. Which configuration change is needed?
Options
- AThe intrusion policy must be disabled for port 80.
- BThe access policy rule must be configured for the action trust.
- CThe NAT policy must be modified to translate the source IP address as well as destination IP
- DThe access policy must allow traffic to the internal web server IP address.
How the community answered
(24 responses)- A4% (1)
- B4% (1)
- C13% (3)
- D79% (19)
Why each option
To make an internal web server reachable from the Internet after NAT, the access policy must explicitly allow traffic to the internal, post-NAT IP address of the server, not just the public IP.
Disabling the intrusion policy would bypass security inspection but does not resolve a fundamental access control block to the internal IP address after NAT.
Setting an access policy rule to 'trust' would bypass deeper inspection but would still require the rule to permit traffic to the correct destination IP after NAT to be effective.
Modifying the NAT policy for source IP translation is irrelevant for incoming connections to a web server where only destination NAT is required.
Even after a NAT policy translates a public IP address to an internal server's IP, the firewall's access policy must then permit traffic to the *internal* destination IP address. If the access policy only allows traffic to the public IP, the traffic will be dropped once its destination is translated to the internal IP, as the internal IP destination is not explicitly permitted by the rule.
Concept tested: Cisco FTD NAT and Access Policy interaction
Source: https://www.cisco.com/c/en/us/td/docs/security/firepower/640/configuration/guide/fpmc-config-guide-v64/nat_for_firepower_threat_defense.html
Topics
Community Discussion
No community discussion yet for this question.